Let's break this down. We're going to add 7142 and 421 together.

Step 1: We'll start by adding the digits 2 & 1 in column 1 and get 3.

Step 2: We'll start by adding the digits 4 & 2 in column 2 and get 6.

Step 3: We'll start by adding the digits 1 & 4 in column 3 and get 5.

Step 4: We'll start by adding the digits 7 & 0 in column 4 and get 7.

So, 7142 + 421 = 7563.

